Filter assemblies of the type generally contemplated by the present invention are commonly employed for pressure filtration in industrial applications and the like. The filter assembly is employed to separate solids from liquids in many different applications including, for example, metal-working coolants, food-processing liquids, chemicals, hazardous wastes, etc.
The filter assembly typically comprises a vertical or horizontal stack of filter plates including at least two filter plates, one of which is mounted to a rigid structure or frame. This assembly is also commonly referred to as a filter press. The filter assembly may include two or more such plates, each adjacent pair of plates being adapted for forming a filter chamber.
A layer of filter media, frequently in the form of long sheet-like rolls, is arranged in the filter chamber between each pair of filter plates. Accordingly, each filter chamber formed between adjacent filter plates includes dirty and clean compartments on opposite sides of the filter media. The dirty compartment receives dirty, contaminated liquid under pressure which is forced through the filter media, thereby depositing the filter cake solid particles (with or without a filter aid) on the filter media. The resultant clean, filtered liquid enters the clean compartment of the adjacent plate. Frequently, such filtration operations are supplemented with the addition of filter aids such as diatomaceous earth and/or Fuller's earth, or other similar products. These filter aids create a filter cake on the filter media which facilitates separation of the super-fine particles and color bodies from the liquid in order to further purify the working fluid in the filter assembly.
Filter assemblies including filter stacks with multiple filter chambers or compartments and employing filter media for separating solid particles from a liquid have been disclosed for example in U.S. Pat. No. 4,274,961 issued Jun. 23, 1981 to Hirs; U.S. Pat. No. 4,289,615 issued Sep. 15, 1981 to Schneider, et al. and U.S. Pat. No. 4,362,617 issued Dec. 7, 1982 to Klepper.
The Schneider, et al. and Klepper references noted above also disclose and discuss representative "extractor devices" which are typically used for replacing filter media in the filter chambers. Used filter media extracted from the filter chambers after use may be collected for storage or disposal or may be cleaned and recycled for subsequent reuse in the filter chamber. Such an extractor for extracting spent filter media from filter chambers and reconditioning it for subsequent reuse in the filter chamber is disclosed for example in application Ser. No. 07/716,646 filed Jun. 17, 1991 by the inventor herein for a FILTER ASSEMBLY WITH FILTER MEDIA RETRIEVAL.
Within filter assemblies of the type generally described above and in similar assemblies employed for other applications, it is necessary to provide means for opening the filter chambers when necessary, to extract and replace filter media as noted above, for maintenance of the filter assemblies and for other functions as well.
Particularly in connection with regularly opening the filter chambers in order to replace the spent filter media and then sequentially closing the filter chambers to allow continued operation of the filter press, it is to be noted that the filter plates forming the filter chambers are typically very heavy, often weighing in the range of several hundred pounds. Accordingly, it is necessary to provide a closer mechanism capable of exerting substantial force in order to maintain the filter assembly in closed and sealed relation. At the same time, it is also desirable to provide suitable controls for the closer mechanism so that it can be readily opened and closed to facilitate extraction and/or replacement of the filter media as well as other possible operations within the filter assembly and then to rapidly close the filter assembly in order to permit continued operation of the filter assembly.
Closer mechanisms for opening and closing filter assemblies have commonly been provided in the past. Many of these closer mechanisms are mechanical devices applying mechanical force to a movable plate. Closer mechanisms of this type are disclosed for example by U.S. Pat. No. 294,133 issued Feb. 26, 1884 to Johnson; U.S. Pat. No. 643,900 issued Feb. 20, 1900 to Hotlinger; U.S. Pat. No. 652,588 issued Jun. 26, 1900 to Boag; U.S. Pat. 1,226,103 issued May 15, 1917 to Merrill; and U.S. Pat. No. 2,076,049 issued Apr. 6, 1937 to Seitz.
A variation of mechanical closer devices as described above may include a hydraulically actuated mechanical closer as disclosed for example in U.S. Pat. No. 1,749,080 issued Mar. 4, 1930 to Mathers.
Generally, mechanical closer mechanisms of the type outlined above are relatively massive and provide limited responsiveness in facilitating opening and closing of the filter assembly during repeated cycles as necessary for example where filter media is to be replaced in the filter chambers. In particular, it has been found difficult and/or expensive to rapidly open filter assemblies when they are operated by such mechanical closer mechanisms.
More recently, closer mechanisms employing inflatable bladders to apply closing force have been disclosed for example in U.S. Pat. No. 3,117,083 issued Jan. 7, 1964 to Przhilensky; U.S. Pat. No. 4,172,790 issued Oct. 30, 1979 to Kubo and more recently U.S. Pat. No. 4,479,426 issued Oct. 30, 1984 to Olenfalk.
Of the above references, the Przhilensky patent disclosed a closer mechanism including a rubber tire configuration as the inflatable bladder. A filter press in the Kubo patetit employed a plurality of inflatable bladders or diaphragms arranged between different elements in the filter press assembly.
In the Olenfalk patent, a single inflatable bladder, referred to as a "lifting tool" was employed with a movable yoke in order to permit its use beneath a number of vertical filter press stacks. The lifting tool was sequentially employed for closing each of the filter stacks which were then maintained in a closed condition by a mechanical lock. Thus, the closer mechanism for the filter press stacks in the Olenfalk patent suffered from some of the same disadvantages discussed above in connection with other mechanically operated closer mechanisms.